Whole-grain foods are supposed to have cardiovascular benefits. When put to the test, does eating whole grains truly make a difference?
The study involved 33 adults younger than 50 (average age 39) who were overweight or obese and did not have cardiovascular disease. For eight weeks they consumed only meals, snacks and drinks provided by the researchers. A few months later, they followed the same procedure for another eight weeks.
During one eight-week period, the participants’ diet included whole-grain wheat and rice (about 100 grams daily); during the other, their diet included refined wheat and rice products. In all other ways, the diets were identical.
A battery of tests before and after each session showed no differences in weight loss and fat loss and similar drops in cholesterol levels. However, diastolic blood pressure dropped by about 8 percent after participants ate whole grains for eight weeks, compared with a 1 percent drop after they ate the refined grains. That created a 10 percent improvement in pulse pressure (the difference between systolic and diastolic blood pressure levels) associated with the whole-grain diet.
Adults. About a third of all Americans have high blood pressure, and just half of them have it under control. Another third of the population has pre-hypertension, meaning that their blood pressure is higher than it should be but not high enough to be labeled hypertension.
High blood pressure often has no symptoms, but it increases the chances of developing heart disease or having a stroke. The researchers noted that the improvement in blood pressure that the study linked to whole-grain consumption correlates to a 40 percent reduction in risk for a fatal stroke and a 30 percent lower risk for dying from heart disease.
The study involved a small number of participants, most of whom were women. Whether eating whole grains would affect blood pressure in people who were not overweight was not tested. The daily intake of whole grains during the whole-grain eating period was roughly double the minimum amount often recommended (48 grams).
November issue of the Journal of Nutrition (jn.nutrition.org).
The research described in Quick Study comes from credible, peer-reviewed journals.